PC-controlled semiconductor tester (2):

CIRCUIT DESCRIPTION, CONSTRUCTION AND SETTING UP

The circuit diagram of the power supply shows that the semiconductor tester
has an on-board step-up voltage converter
that is powered from the 12-V supply in the
PC. The 5-V supply of the PC is also used to
power certain parts of the circuit. The 12-V
supply of the PC is connected to a step-up
converter via a 4-way connector as used for
floppy disks and hard disks. The current requirement
of the 12-V input is about 2.2 A. If
this current is not available in your PC, it is
still possible to use the semiconductor tester
with a correspondingly reduced maximum
collector current for the device under test.
The input current of the voltage doubler in
the power supply is about 2.2 times the output
current. Hence the 2.2 A input current
requirement if a maximum collector current
of 1 A is to be achieved. The quiescent current
drawn by the power supply is about
150 mA.